How do they work offline? Say you are jogging, and listening to music on the Apple Watch with your iPhone at home, will double-tap no longer work?

Siri requires internet connectivity, and as the only control of this device is the double tap, how will they work when used offline? Will the double-tap fallback to voice control, or will it just attempt to use siri and time out. I am wanting to get these for use with my Apple Watch, and leave my phone at home when I go for walks, it will be crazy if the double-tap is not supported in this circumstance.